Before I got LASIK, I wore contacts but travelled with glasses. There are a huger variety of reasons that you might use contacts even if you have your glasses available. In fact, everyone I know with contacts also always has a pair of glasses that goes with them on travels.

In my case I worked onboard tall ships. Contacts let me be on deck in inclement weather without worrying about spray, fog, or losing a pair of glasses, let me use any pair of sunglasses instead of a ~$250+ pair of prescription glasses, as well as things like diving and snorkelling without needing a $150 prescription mask.